The importance of altered beta-cell function in the primary pathophysiology of non-insulin dependent diabetes is uncertain. The proposed studies aim to test the hypothesis that states of glucose intolerance are characterized by: 1. alterations in the relationships between glucose and insulin secretion, 2. reduced insulin secretory responses to non-glucose secretogogues which act at different points in the insulin secretory cascade and 3. reductions in the ability of the beta-cell to adapt normally to the presence of insulin resistance or mild hyperglycemia.